Caused by: java.sql.SQLException: Trying to connect with ssl, but ssl not enabled in the server

    其实这个问题是意外发现的，前面一篇博客因为数据库配置的最大连接数只有200导致连接失败，在尝试解决问题的时候，看到有人说可以修改springboot配置文件application.yml文件中的datasources的url中的useSSL=false 为useSSL=true,来解决连接的问题，病急乱投医啊，试了试就出现了下面的问题咯~~~

2021-01-22 07:54:03.920 [main] ERROR org.apache.tomcat.jdbc.pool.ConnectionPool - Unable to create initial connections of pool.
java.sql.SQLException: Trying to connect with ssl, but ssl not enabled in the server
        at org.mariadb.jdbc.internal.util.ExceptionMapper.get(ExceptionMapper.java:136)
        at org.mariadb.jdbc.internal.util.ExceptionMapper.throwException(ExceptionMapper.java:69)
        at org.mariadb.jdbc.Driver.connect(Driver.java:109)
        at org.apache.tomcat.jdbc.pool.PooledConnection.connectUsingDriver(PooledConnection.java:310)
        at org.apache.tomcat.jdbc.pool.PooledConnection.connect(PooledConnection.java:203)
        at org.apache.tomcat.jdbc.pool.ConnectionPool.createConnection(ConnectionPool.java:735)
        at org.apache.tomcat.jdbc.pool.ConnectionPool.borrowConnection(ConnectionPool.java:667)
        at org.apache.tomcat.jdbc.pool.ConnectionPool.init(ConnectionPool.java:482)
        at org.apache.tomcat.jdbc.pool.ConnectionPool.<init>(ConnectionPool.java:154)
        at org.apache.tomcat.jdbc.pool.DataSourceProxy.pCreatePool(DataSourceProxy.java:118)
        at org.apache.tomcat.jdbc.pool.DataSourceProxy.createPool(DataSourceProxy.java:107)
        at org.apache.tomcat.jdbc.pool.DataSourceProxy.getConnection(DataSourceProxy.java:131)
        at org.springframework.jdbc.datasource.DataSourceUtils.doGetConnection(DataSourceUtils.java:111)
        at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(DataSourceUtils.java:77)
        at org.springframework.jdbc.support.JdbcUtils.extractDatabaseMetaData(JdbcUtils.java:325)
        at org.springframework.jdbc.support.JdbcUtils.extractDatabaseMetaData(JdbcUtils.java:365)
        at org.springframework.boot.autoconfigure.orm.jpa.DatabaseLookup.getDatabase(DatabaseLookup.java:72)
        at org.springframework.boot.autoconfigure.orm.jpa.JpaProperties.determineDatabase(JpaProperties.java:139)
        at org.springframework.boot.autoconfigure.orm.jpa.JpaBaseConfiguration.jpaVendorAdapter(JpaBaseConfiguration.java:105)
        at org.springframework.boot.autoconfigure.orm.jpa.HibernateJpaAutoConfiguration$$EnhancerBySpringCGLIB$$bb232614.CGLIB$jpaVendorAdapter$4(<generated>)

。。。 。。。

Caused by: org.springframework.jdbc.CannotGetJdbcConnectionException: Could not get JDBC Connection; nested exception is java.sql.SQLException: Trying to connect with ssl, but ssl not enabled in the server
        at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(DataSourceUtils.java:80)
        at org.springframework.jdbc.support.JdbcUtils.extractDatabaseMetaData(JdbcUtils.java:325)
        ... 69 common frames omitted
Caused by: java.sql.SQLException: Trying to connect with ssl, but ssl not enabled in the server
        at org.mariadb.jdbc.internal.util.ExceptionMapper.get(ExceptionMapper.java:136)
        at org.mariadb.jdbc.internal.util.ExceptionMapper.throwException(ExceptionMapper.java:69)
        at org.mariadb.jdbc.Driver.connect(Driver.java:109)
        at org.apache.tomcat.jdbc.pool.PooledConnection.connectUsingDriver(PooledConnection.java:310)
        at org.apache.tomcat.jdbc.pool.PooledConnection.connect(PooledConnection.java:203)
        at org.apache.tomcat.jdbc.pool.ConnectionPool.createConnection(ConnectionPool.java:735)
        at org.apache.tomcat.jdbc.pool.ConnectionPool.borrowConnection(ConnectionPool.java:667)
        at org.apache.tomcat.jdbc.pool.ConnectionPool.init(ConnectionPool.java:482)
        at org.apache.tomcat.jdbc.pool.ConnectionPool.<init>(ConnectionPool.java:154)
        at org.apache.tomcat.jdbc.pool.DataSourceProxy.pCreatePool(DataSourceProxy.java:118)
        at org.apache.tomcat.jdbc.pool.DataSourceProxy.createPool(DataSourceProxy.java:107)
        at org.apache.tomcat.jdbc.pool.DataSourceProxy.getConnection(DataSourceProxy.java:131)
        at org.springframework.jdbc.datasource.DataSourceUtils.doGetConnection(DataSourceUtils.java:111)
        at org.springframework.jdbc.datasource.DataSourceUtils.getConnection(DataSourceUtils.java:77)
        ... 70 common frames omitted
Caused by: org.mariadb.jdbc.internal.util.dao.QueryException: Trying to connect with ssl, but ssl not enabled in the server
        at org.mariadb.jdbc.internal.protocol.AbstractConnectProtocol.handleConnectionPhases(AbstractConnectProtocol.java:462)
        at org.mariadb.jdbc.internal.protocol.AbstractConnectProtocol.connect(AbstractConnectProtocol.java:369)
        at org.mariadb.jdbc.internal.protocol.AbstractConnectProtocol.connectWithoutProxy(AbstractConnectProtocol.java:755)
        at org.mariadb.jdbc.internal.util.Utils.retrieveProxy(Utils.java:468)
        at org.mariadb.jdbc.Driver.connect(Driver.java:104)
        ... 81 common frames omitted

    当然啦，最后问题的真正原因还是找到了，跟useSSL=false这个参数是没有任何关系的，尽管走了弯路，但是毕竟实践出真知嘛，不亏不亏~~~

    如：

url: jdbc:mariadb://127.0.0.1:3306/iot?createDatabaseIfNotExist=true&useSSL=false&useUnicode=true&characterEncoding=utf-8&zeroDateTimeBehavior=convertToNull&transformedBitIsBoolean=true&autoReconnect=true&failOverReadOnly=false

C3P0连接池配置一些参数

参数名称	参数说明
user	数据库用户名（用于连接数据库）
password	用户密码（用于连接数据库）
useUnicode	是否使用Unicode字符集，如果参数characterEncoding设置为gb2312或gbk，本参数值必须设置为true
characterEncoding	当useUnicode设置为true时，指定字符编码。比如可设置为gb2312或gbk
autoReconnect	当数据库连接异常中断时，是否自动重新连接？
autoReconnectForPools	是否使用针对数据库连接池的重连策略
failOverReadOnly	自动重连成功后，连接是否设置为只读？
maxReconnects	autoReconnect设置为true时，重试连接的次数
initialTimeout	autoReconnect设置为true时，两次重连之间的时间间隔，单位：秒
connectTimeout	和数据库服务器建立socket连接时的超时，单位：毫秒。 0表示永不超时，适用于JDK 1.4及更高版本
socketTimeout	socket操作（读写）超时，单位：毫秒。 0表示永不超时